Yes,
I think FFA would work best with matchmaking, but it requires players to be very close in skill. It's much easier to make a balanced team game than to make a balanced FFA. I don't think a FFA matchmaker should make a match where the top rank has distance more than one to the bottom rank. Technically, FFA has the ability to be balanced for all ranks, and its balance isn't tied to how well you play. What it really needs is the ability to communicate well and to do so even while fighting under pressure. Balance is much easier though when players are naturally even in skill.
and no.
With the current MM activity I doubt we could get enough players of the same rank to join at the same time. I'm also not sure we could even create good FFA matches just by matching MM rating. A FFA rating would definitely make sense, but that comes with many other problems. There are also many types of FFA such that the matchmaker will probably never make what you are looking for. I.e. some players just want a 16 way lobster pot on an asymmetric map with half of the players getting rushed or 2v1ed in the first few minutes, some want a small map with aggressive 1v1 style play from the start and some want to sit back on a large map with everyone building their pretty castle.
I also have the feeling that the current MM situation is a bit misleading UI. There are four different MM buttons for a new player to choose from, two, maybe three of which will likely cause the player to leave before they ever find a match. Chobby's main advantage was that it makes it easier to get into a game and reduces the number of ways to get stuck in some obscure spads autohost. I know this might sound a bit antagonistic, but ZK's first play experience is still a far distance from "industry standard".